Light modulators of many kinds are presently in use. Many require expensive equipment to activate, such as cathode ray tube devices, motors, etc. Some modulators are comprised of a deflectable membrane, which is only momentarily deformed when energized.
Visual displays of many kinds are presently in use. One of the most common forms of visual presentation uses the cathode ray tube as the means of presenting data. Various forms of this device are in general use. Another device is the electroluminescent panel. This device is finding increasing usage, but all the faults and deficiencies of the system have not been corrected. Arrays of lamps, light generating diodes, liquid crystal displays and other devices have been developed and are in use.
In the present state of the art the devices for presenting data require a continuous supply of energy to operate properly. The image on the screen of the cathode ray tube will disappear unless "refreshed" periodically. The information for the refresh must be supplied by some device which can "remember" the data, such as core storage, magnetic discs and tapes. This results in complex and costly equipment.
"Nixie" tubes, light emitting diodes, etc. are used for "character" displays. Their use has generally been limited by the need of having expensive electronic ancillary devices (with internal transistorized storage) to activate these elements. In addition many of the devices have a display of low intensity and therefore limited visibility.